Camshafts are used in internal combustion engines in order to actuate gas exchange valves. The camshaft in an internal combustion engine includes a plurality of cams that engage cam followers (i.e. bucket tappets, finger levers or rocker arms). When the camshaft rotates, the cams lift or depress the cam followers which in turn actuate gas exchange valves (intake, exhaust). The position and shape of the cams dictate the opening period and amplitude as well as the opening and closing time of the gas exchange valves.
Camshaft phasers are used to advance or retard the opening or closing period, phasing the camshaft with respect to the crankshaft rotation. Camshaft phasers generally comprise a timing gear, which can be a chain, belt or gear wheel connected in fixed rotation to a crankshaft by a chain, belt or gear drive, respectively, acting as an input to the phaser. The phaser includes an output connection to the camshaft. A phasing input is also provided in the form of a hydraulic, pneumatic or electric drive in order to phase or adjust the output rotation of the camshaft relative to the input rotation of the crankshaft.
Camshaft phasers are generally known in two forms, a piston-type phaser with an axially displaceable piston and a vane-type phaser with vanes that can be acted upon and pivoted in the circumferential direction. With either type, the camshaft phaser is fixedly mounted on the end of a camshaft. An example mounting may be performed as disclosed in U.S. Pat. No. 6,363,896, entitled “Camshaft Adjuster for Internal Combustion Engines”, by Wolfgang Speier, issued on Apr. 2, 2002, using a clamping screw forming the element of the camshaft phaser that effects centering relative to the camshaft.
Camshaft phasers that operate according to the vane-cell principle for use on single camshafts are known in the art. U.S. Pat. No. 6,805,080, entitled “Device for changing the control times of gas exchange valves of internal combustion engines, particularly rotary piston adjustment device for rotation angle adjustment of a camshaft relative to a crankshaft”, by Eduard Golovatai-Schmidt et al., issued on Oct. 19, 2004, generally shows a construction of a vane-cell type camshaft phaser for use in an internal combustion engine. These single camshaft phasers are commonly used on dual overhead cam (DOHC) engines where intake and exhaust cam lobes are located on separate intake and exhaust camshafts.
It is known to receive oil for chambers in a camshaft phaser, formed by a rotor and a stator for the phaser and used to control phasing of the phaser, in radially aligned channels opening to a radially central space. However, the requirement for a radially central space increases both the radial extent of the phaser and limits the spaces into which the phaser can be installed as well as the options for supplying oil to the chambers. With increasing engine sizes and decreasing space in engine compartments, axial and radial space is becoming limited, sometimes requiring multi-piece phaser assemblies in order to assemble a phaser in position. Commonly-owned co-pending patent application No. 61/824,033 discloses a phaser section including a stator non-rotatably connected to the drive sprocket, a rotor at least partially rotatable with respect to the stator and a rotor extension non-rotatably connected to the rotor, and a plurality of chambers formed by the rotor and the stator; and a rotor nose separately formed from the phaser section and non-rotatably connected to the phaser section, extending past a front side of the phaser section in a first axial direction. The rotor nose and rotor plate or extension are separately assembled and allow for assembly of the cam phaser assembly onto engines with restricted axial and radial space. U.S. patent application No. 61/824,033 is incorporated herein by reference.
U.S. Pat. No. 7,409,935 discloses a method and apparatus for setting a bias or return spring load during assembly of a camshaft phaser. A spring retainer is used with a first end of a bias spring engaged in a notch, the spring wrapped around the spring retainer and secured at a second end by an eccentric bolt or fastener. The spring is wound about the spring retainer and the spring retainer, in turn is secured to the rotor of the cam phaser. Where there is limited axial and radial space, such a separate component, such as a spring retainer can not be utilized. A method and apparatus for attaching and winding the return spring in a multi-piece phaser assembly is needed.